1. Field of the Invention
This invention relates in general to wire carriers and edge protector trim strips formed therefrom. More particularly, this invention relates to an improved wire carrier in which the strands of material interwoven with the wire are selectively positioned transversely of the carrier. Selective positioning of the strands achieves increased resistance of the carrier to hydraulic deformation during extrusion of an elastomeric material onto the carrier. Selective strand positioning also minimizes damage to center strands of material when the carrier is formed or bent into a channel-shaped carrier.
2. Description of the Prior Art
Lansing, U.S. Pat. No. 3,198,689 discloses an edge protector trim strip comprising a flat wire carrier formed from a continuous wire looped to form lengths extending transversely and spaced from one another longitudinally of the strip. The wire lengths are stayed and maintained in their spaced relation with one another by interweaving with them a plurality of strands of material randomly located transversely of the wire lengths from one edge to the other. In Lansing, the wire carrier is coated with an elastomeric material while in a flat condition. After the coating operation, the flat coated wire carrier is formed by form rolls into a trim strip of substantially U-shaped transverse cross section.
During the trim strip forming step, the strands of material located at the bends or corners of the U-shaped strip are embedded in elastomeric material and hence are not damaged by the form rolls. Other problems arose, however, such as subjecting the elastomeric material in the bent areas of the trim strip to continuous stress in its relaxed state resulting, for example, in reduced useful life of the trim strip. To overcome this problem, the trim strip manufacturing process was changed by feeding the flat, uncoated wire carrier through form rolls to form a channel-shaped wire carrier of substantially U-shape transverse cross section. The formed wire carrier was then fed through an extruder where an elastomeric material was coated onto the wire carrier to form a trim strip in which the elastomeric material is free from stress in its relaxed state. Although the changed manufacturing process solved one problem, another problem developed which still persists, namely damage to strands of material located in the bend areas of the carrier during the carrier forming operation. This problem was made more difficult by the tendency of the woven strands to slide laterally or sidewise on the wire lengths into the bend areas.
Still another long standing, persistent problem resulting from the above change in manufacturing operation was a reduction in the stability of the wire carrier during the elastomeric extruding operation, particularly along the edges thereof, resulting in the formation of a defective trim strip, or strip of lower quality. The hydraulic forces generated during the extrusion process cause the wire carrier to deform by, for example, the looped ends thereof bending back as they pass through the extruder. This wire carrier deformation or distortion is increased if the single strand along each edge inadvertently slides toward the center of the wire carrier.